<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="5.css">
    <script src="5.js"></script>
</head>

<body>
    <script>
        "use strict" // 使用严格模式，强制各种声明约束
        // web = "baidu.com";
        // console.log(web);
        // function show(){
        //     web = "baidu.com";
        // }

        var web = "baidu.com";
        show();
        console.log(web);
    </script>
</body>
<button id="size-12">12</button>
<button id="size-14">14</button>
<button id="size-16">16</button>
<p>Some paragraph text</p>
<h1>some heading 1 text</h1>
<h2>some heading 2 text</h2>

</html>